Vitamin D3 up-regulated protein 1(VDUP1) is regulated by FOXO3A and miR-17-5p at the transcriptional and post-transcriptional levels, respectively, in senescent fibroblasts

H3K18 lactylation of senescent microglia potentiates brain aging and Alzheimer's disease through the NFκB signaling pathway

Cellular senescence serves as a fundamental and underlying activity that drives the aging process, and it is intricately associated with numerous age-related diseases, including Alzheimer's disease (AD), a neurodegenerative aging-related disorder characterized by progressive cognitive impairment. Although increasing evidence suggests that senescent microglia play a role in the pathogenesis of AD, their exact role remains unclear. In this study, we quantified the levels of lactic acid in senescent microglia, and hippocampus tissues of naturally aged mice and AD mice models (FAD4T and APP/PS1). We found lactic acid levels were significantly elevated in these cells and tissues compared to their corresponding counterparts, which increased the level of pan histone lysine lactylation (Kla). We aslo identified all histone Kla sites in senescent microglia, and found that both the H3K18 lactylation (H3K18la) and Pan-Kla were significantly up-regulated in senescent microglia and hippocampus tissues of naturally aged mice and AD modeling mice. We demonstrated that enhanced H3K18la directly stimulates the NFκB signaling pathway by increasing binding to the promoter of Rela (p65) and NFκB1(p50), thereby upregulating senescence-associated secretory phenotype (SASP) components IL-6 and IL-8. Our study provides novel insights into the physiological function of Kla and the epigenetic regulatory mechanism that regulates brain aging and AD. Specifically, we have identified the H3K18la/NFκB axis as a critical player in this process by modulating IL-6 and IL-8. Targeting this axis may be a potential therapeutic strategy for delaying aging and AD by blunting SASP.

Integration single-cell and bulk RNA-sequencing data to reveal senescence gene expression profiles in heart failure

Background

Heart failure (HF) represents one of healthcare's biggest challenges. Although rarely noticed, aging is a crucial risk factor for cardiovascular disease. Our study aims to reveal aging's role in HF by integrating single-cell RNA-sequencing (scRNA-seq) and bulk RNA-sequencing databases.

Methods

We collected HF heart sample data from the Gene Expression Omnibus database and senescence gene data from CellAge. The FindCluster () package was used for cell cluster analysis. Differentially expressed genes (DEG) were identified operating the FindMarkers function. Cell activity score calculation was performed using the AUCell package. UpSetR plotted the intersection between DEGs of active cell types, bulk data DEGs, and genes associated with aging. Using the DGIdb database gene-drug interaction data, we search for potential targeted therapeutics based on common senescence genes.

Results

The scRNA-seq data revealed myocardial heterogeneity in HF tissues. A series of crucial common senescence genes were found. The senescence gene expression profile hints at an intriguing connection between monocytes and HF. After analyzing the DEGs in the bulk dataset, the DEGs in scRNA-seq, the DEGs in each active cell type, and senescence genes, we identified ten genes as common senescence genes present in HF. Correlation analysis of transcriptomics, proteomics, and ceRNA was performed to provide ideas for future studies individually. Moreover, we discovered that common senescence genes and potential therapeutic drugs interact among different cell types. Further research is needed on the expression pattern of senescence genes and molecular regulation in HF.

Conclusions

In summary, we identified the functional significance of the senescence gene in HF using integrated data. It is possible that this more profound understanding of how senescence contributes to the development of HF will aid in unraveling the mechanisms that promote the disease and provide hints for developing therapeutics.

Thioredoxin-Interacting Protein in Cancer and Diabetes

Significance: Thioredoxin-interacting protein (Txnip) is an α-arrestin protein that acts as a cancer suppressor. Txnip is simultaneously a critical regulator of energy metabolism. Other alpha-arrestin proteins also play key roles in cell biology and cancer. Recent Advances: Txnip expression is regulated by multilayered mechanisms, including transcriptional regulation, microRNA, messenger RNA (mRNA) stabilization, and protein degradation. The Txnip-based connection between cancer and metabolism has been widely recognized. Meanwhile, new aspects are proposed for the mechanism of action of Txnip, including the regulation of RNA expression and autophagy. Arrestin domain containing 3 (ARRDC3), another α-arrestin protein, regulates endocytosis and signaling, whereas ARRDC1 and ARRDC4 regulate extracellular vesicle formation. Critical Issues: The mechanism of action of Txnip is yet to be elucidated. The regulation of intracellular protein trafficking by arrestin family proteins has opened an emerging field of biology and medical research, which needs to be examined further. Future Directions: A fundamental understanding of the mechanism of action of Txnip and other arrestin family members needs to be explored in the future to combat diseases such as cancer and diabetes. Antioxid. Redox Signal. 36, 1001-1022.

Genistein alleviates H2O2-induced senescence of human umbilical vein endothelial cells via regulating the TXNIP/NLRP3 axis

CONTEXT

Genistein (Gen) has shown protective effects against ageing process.

OBJECTIVE

To explore the role of Gen on the senescence of H₂O₂-induced human umbilical vein endothelial cells (HUVECs) and investigate the possible mechanism.

MATERIALS AND METHODS

HUVECs were treated with different concentrations of H₂O₂ (50, 100, 200 and 400 μmol/L) for 1 h or Gen administration (20, 40, 80 and 160 μg/mL) for 24 h. Functional experiments (cell counting kit-8, β-galactosidase staining and flow cytometry) were used to detect the effect of Gen on H₂O₂-induced HUVECs. After HUVECs were transfected with TXNIP overexpression plasmids, the expression of p16, p21, thioredoxin-interacting protein (TXNIP), nucleotide-binding and oligomerization domain-like receptor 3 (NLRP3), cleaved caspase-3 and cleaved caspase-1 in HUVECs were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot.

RESULTS

H₂O₂ (200 and 400 μmol/L) inhibited the proliferation of HUVECs. At concentrations of >50 μmol/L, H₂O₂ induced the cell cycle progression arrests in G1 phase and promoted cell senescence of HUVECs. Gen had no obvious cytotoxicity to HUVECs below 160 µg/mL. H₂O₂-induced HUVEC senescence and the expression of TXNIP and NLRP3 in HUVECs were down-regulated by Gen (40 and 80 µg/mL). Expressions of TXNIP and NLRP3 in HUVECs were up-regulated by H₂O₂ but down-regulated by Gen. Overexpressed TXNIP partially reversed the suppressive effect of Gen on H₂O₂-induced senescence and apoptosis of HUVECs. Expressions of p16, p21, TXNIP, NLRP3, cleaved caspase-3 and cleaved caspase-1 in H₂O₂-treated HUVECs were inhibited by Gen, while the inhibition as such was partially reversed by overexpressed TXNIP.

DISCUSSION AND CONCLUSIONS

H₂O₂-induced HUVEC senescence was alleviated by Gen via suppressing the TXNIP/NLRP3 axis, which may offer a potential therapeutic approach for improving HUVEC senescence and provide a new direction for the treatment of cardiovascular disease.

Vitamin D promotes autophagy in AML cells by inhibiting miR-17-5p-induced Beclin-1 overexpression

MicroRNA (miR)-17-5p has been investigated in many diseases as a regulator of disease progression and is highly expressed in acute myeloid leukemia (AML). However, potential mechanisms underlying the function of miR-17-5p in AML need more elucidation. MiR-17-5p expression was augmented, while 25(OH)D3 and Beclin-1 levels were decreased in AML patients with the highest risk for disease progression. MiR-17-5p, 25(OH)D3 and Beclin-1 were determined to be clinically important in AML based on ROC curve analysis. Higher miR-17-5p expression as well as lower 25(OH)D3 and Beclin-1 expression were relevant with poor prognosis in AML. In addition, miR-17-5p was negatively correlated with and bound to BECN1. Vitamin D was found to diminish cell proliferation and enhance autophagy. Finally, through rescue assays, miR-17-5p facilitated the ability of cell proliferation, inhibited autophagy and apoptosis by modulating Beclin-1 in HL-60 cells following the treatment of 4 μM vitamin D. Vitamin D promoted autophagy in AML cells by modulating miR-17-5p and Beclin-1.

Vitamin D and Non-coding RNAs: New Insights into the Regulation of Breast Cancer

Breast cancer, a life-threatening serious disease with a high incident rate among women, is responsible for thousands of cancer-associated death worldwide. Numerous investigations have evaluated the possible mechanisms related to this malignancy. Among them, non-coding RNAs (ncRNAs), i.e., microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNAs have recently attracted attention of researchers. In addition to recent studies for evaluating the role of ncRNAs in breast cancer etiology, some investigations have revealed that vitamin D has regulatory and therapeutic roles in breast cancer. Moreover, an important link between vitamin D and ncRNAs in cancer therapy has been highlighted. Herein, the aim of this study was to discuss the available data on the mentioned link in breast cancer.

Senescent Cell-Secreted Netrin-1 Modulates Aging-Related Disorders by Recruiting Sympathetic Fibers

Cellular senescence is implicated in several lines of aging-related disorders. However, the potential molecular mechanisms by which cellular senescence modulates age-related pathologies remain largely unexplored. Herein, we report that the density of sympathetic fibers (SFs) is significantly elevated in naturally aged mouse tissues and human colon adenoma tissues compared to the SFs densities in the corresponding young mouse tissues and human non-lesion colon tissues. A dorsal root ganglion (DRG)-human diploid fibroblast coculture assay revealed that senescent cells promote the outgrowth of SFs, indicating that the senescent cells induce recruitment of SFs in vitro. Additionally, subcutaneous transplantation of 2BS fibroblasts in nude mice shows that transplanted senescent 2BS fibroblasts promote SFs infiltration. Intra-articular senolytic molecular injection can reduce SFs density and inhibit SFs infiltration caused by senescent cells in osteoarthritis (OA), suggesting senescent cells promote the infiltration of SFs in vivo in aged tissues. Notably, the elevated level of SFs contributes to impaired cognitive function in naturally aged mice, which can be reversed by treatment with propranolol hydrochloride, a non-selective β receptor blocker that inhibits sympathetic nerve activity (SNA) by blocking non-selective β receptors. Additionally, 6-hydroxydopamine (6-OHDA)-induced sympathectomy improved hepatic sympathetic overactivity mediated hepatic steatosis in high fat diet (HFD)-fed APOE knockout mice (APOE^−/− mice) by reducing hepatic SNA. Taken together, this study concludes that senescent cell-secreted netrin-1 mediated SFs outgrowth and infiltration, which contributes to aging-related disorders, suggesting that clearing senescent cells or inhibiting SNA is a promising therapeutic strategy for improving sympathetic nervous system (SNS) hyperactivity-induced aging-related pathologies.

miR-93, miR-373, and miR-17-5p Negatively Regulate the Expression of TBP2 in Lung Cancer

Recently, several miRNAs have been revealed to play critical roles in oncogenesis and tumor progression of many cancers. Thioredoxin-1 (Trx-1) binding protein-2 (TBP-2) is an internal inhibitor of Trx-1, which plays the role in regulating oxidative stress, inhibiting cell growth, and promoting apoptosis. The expression of TBP-2 is usually decreased in cancer tissues. However, whether the miRNAs regulate the TBP-2 expression in lung cancer is still unclear. In this study, we examined the levels of TBP-2, miR-93, miR-373, and miR-17-5p in lung cancer tissues and their adjacent normal lung tissues of 36 patients. We found that the expressions of miR-93, miR-373, and miR-17-5p were higher, whereas the expression of TBP-2 mRNA and protein was significantly lower in lung cancer tissues compared with adjacent normal lung tissues. After the three miRNA mimics were transfected in the lung cancer cells, NCI-H460, the level of TBP-2 mRNA and TBP-2 protein was decreased. Then, the anti-cancer drug 5-fluorouracil was used to stimulate the NCI-H460 cells; the mRNA levels of miR-93, miR-373, and miR-17-5p were decreased, and the level of TBP-2 mRNA and protein was increased. Collectively, the above results suggest that miR-93, miR-373, and miR-17-5p negatively regulate the TBP-2 expression in lung cancer. This study may provide therapeutic targets with lung cancer.

p16 promotes proliferation in cervical carcinoma cells through CDK6-HuR-IL1A axis

The Cyclin-Dependent Kinase Inhibitor p16 (p16) acts as a tumor suppressor in most cells, but for HPV transformed cervical cancer, in which oncoprotein E7 expressed by human papillomavirus (HPV) mediates the degradation of retinoblastoma protein (Rb), p16 exhibits oncogenic activity. Our study was conducted to study the mechanism underling p16 mediated promoting effect of cell proliferation in cervical cancer cell lines. CCK8 assay and EdU incorporation were conducted to evaluate cell proliferation. Loss-of-function assay was used to silence p16 in Ca Ski and SiHa cells. Next, western blot, qPCR, RNA silencing, luciferase activity assay, run-on assay, mRNA stability assay, RNA immunoprecipitation, co-immunoprecipitation Immunofluorescence were performed to examine the interaction between CDK6, HuR, and IL1A mRNA in p16 mediated proliferation promoting effect. Our results showed that: (1) Silencing p16 inhibited the proliferation of cervical cancer cells by decreasing the half-life of IL1A mRNA in CDK6 dependent manner; (2) The stabilization of IL1A mRNA was regulated by HuR which could be inactivated by p16/CDK6 mediated phosphorylation at Ser202; (3) IL1A mediated the oncogenic activity of p16 in cervical carcinoma cell lines. In conclusion, p16 promotes proliferation in cervical carcinoma cells through CDK6-HuR-IL1A axis.

Circular RNA CircCCNB1 sponges micro RNA-449a to inhibit cellular senescence by targeting CCNE2

Circular RNAs (CircRNAs) are a novel subset of non-coding RNA widely present in eukaryotes that play a central role in physiological and pathological conditions. Accumulating evidence has indicated that CircRNAs participated in modulating tumorigenesis by acting as a competing endogenous RNA (CeRNA). However, the roles and functions of CircRNAs in cellular senescence and aging of organisms remain largely obscure. We performed whole transcriptome sequencing to compare the expression patterns of circular RNAs in young and prematurely senescent human diploid fibroblast 2BS cells, and identified senescence-associated circRNAs (SAC-RNAs). Among these SAC-RNAs, we observed the significantly downregulated expression of CircRNAs originating from exons 6 and 7 circularization of the cyclin B1 gene (CCNB1), termed CircCCNB1. Reduced CircCCNB1 expression triggered senescence in young 2BS cells, as measured by increased senescence associated-beta-galactosidase (SA-β-gal) activity, enhanced expression of cyclin-dependent kinase inhibitor 1A (CDKN1A)/P21 and tumor protein 53 (TP53) expression, and reduced cell proliferation. Mechanistically, reduced CircCCNB1 level inhibited cyclin E2 (CCNE2) expression by modulating micro RNA (miR)-449a activity, which repressed cellular proliferation. Our data suggested that CircCCNB1may serve as a sponge against miR-449a to delay cellular senescence by targeting CCNE2. Targeting CircCCNB1 may represent a promising strategy for aging and age-related disease interventions. Furthermore, we also identified and characterized several kinds of the CircCCNB1-binding proteins (CBPs), which may contribute to the degradation of CircCCNB1.

The Oncogene PIM1 Contributes to Cellular Senescence by Phosphorylating Staphylococcal Nuclease Domain-Containing Protein 1 (SND1)

Background

The oncogene PIM1, encoding a constitutively active serine/threonine protein kinase, is involved in the regulation of cell proliferation, survival, differentiation, and apoptosis. There is a growing body of literature on the role of PIM1-mediated cellular senescence, but the precise mechanism remains unclear.

Material/Methods

Silver staining and LC–MS/MS analysis were performed to investigate the protein interacting with PIM1. Immunofluorescence, Co-IP, and Western blot assay were used to assess the interaction of PIM1 and SND1. EdU incorporation and CCK8 assay were used to detect cell proliferation and immunohistochemistry was used to detect the level of the indicated protein.

Results

We found that PIM1 can bind directly and phosphorylate SND1. In addition, decreased expression of SND1 leads to the upregulation of SASP. SND1 is involved in cellular senescence induced by PIM1.

Conclusions

We investigated the role of PIM1 in oncogene-induced normal cellular senescence. Our results promote further understanding of the mechanisms underlying OIS and suggest potential applications for preventing tumorigenesis.

Metabolic Syndrome, Brain Insulin Resistance, and Alzheimer's Disease: Thioredoxin Interacting Protein (TXNIP) and Inflammasome as Core Amplifiers

Empirical evidence indicates a strong association between insulin resistance and pathological alterations related to Alzheimer's disease (AD) in different cerebral regions. While cerebral insulin resistance is not essentially parallel with systemic metabolic derangements, type 2 diabetes mellitus (T2DM) has been established as a risk factor for AD. The circulating "toxic metabolites" emerging in metabolic syndrome may engage several biochemical pathways to promote oxidative stress and neuroinflammation leading to impair insulin function in the brain or "type 3 diabetes". Thioredoxin-interacting protein (TXNIP) as an intracellular amplifier of oxidative stress and inflammasome activation may presumably mediate central insulin resistance. Emerging data including those from our recent studies has demonstrated a sharp TXNIP upregulation in stroke, aging and AD and well underlining the significance of this hypothesis. With the main interest to illustrate TXNIP place in type 3 diabetes, the present review primarily briefs the potential mechanisms contributing to cerebral insulin resistance in a metabolically deranged environment. Then with a particular focus on plausible TXNIP functions to drive and associate with AD pathology, we present the most recent evidence supporting TXNIP as a promising therapeutic target in AD as an age-associated dementia.

Honokiol antagonizes doxorubicin‑induced cardiomyocyte senescence by inhibiting TXNIP‑mediated NLRP3 inflammasome activation

Senescence of cardiomyocytes is considered a key factor for the occurrence of doxorubicin (Dox)‑associated cardiomyopathy. The NOD‑like receptor family pyrin domain‑containing 3 (NLRP3) inflammasome is reported to be involved in the process of cellular senescence. Furthermore, thioredoxin‑interactive protein (TXNIP) is required for NLRP3 inflammasome activation and is considered to be a key component in the regulation of the pathogenesis of senescence. Studies have demonstrated that pretreatment with honokiol (Hnk) can alleviate Dox‑induced cardiotoxicity. However, the impact of Hnk on cardiomyocyte senescence elicited by Dox and the underlying mechanisms remain unclear. The present study demonstrated that Hnk was able to prevent Dox‑induced senescence of H9c2 cardiomyocytes, indicated by decreased senescence‑associated β‑galactosidase (SA‑β‑gal) staining, as well as decreased expression of p16INK4A and p21. Hnk also inhibited TXNIP expression and NLRP3 inflammasome activation in Dox‑stimulated H9c2 cardiomyocytes. When TXNIP expression was enforced by adenovirus‑mediated gene overexpression, the NLRP3 inflammasome was activated, which led to inhibition of the anti‑inflammation and anti‑senescence effects of Hnk on H9c2 cardiomyocytes under Dox treatment. Furthermore, adenovirus‑mediated TXNIP‑silencing inhibited the NLRP3 inflammasome. Consistently, TXNIP knockdown enhanced the anti‑inflammation and anti‑senescence effects of Hnk on H9c2 cardiomyocytes under Dox stimulation. In summary, Hnk was found to be effective in protecting cardiomyocytes against Dox‑stimulated senescence. This protective effect was mediated via the inhibition of TXNIP expression and the subsequent suppression of the NLRP3 inflammasome. These results demonstrated that Hnk may be of value as a cardioprotective drug by inhibiting cardiomyocyte senescence.

PIM1-catalyzed CBX8 phosphorylation promotes the oncogene-induced senescence of human diploid fibroblast

The proto-oncogene PIM1 encodes Ser/Thr kinase and regulates cell growth, differentiation and apoptosis. However, more and more studies including ours have found that PIM1 can induce senescence in normal human diploid fibroblasts and behave as a tumor suppressor. But the relevant molecular mechanism of this process is not yet clear. It has been reported that Chromobox homolog 8 (CBX8) binds directly to INK4A as a transcriptional repressor, thereby suppressing stress-induced senescence. Here we report that PIM1 can phosphorylate CBX8 to promote its degradation, thereby up-regulating p16, during PIM1-induced cell senescence. Overexpression of CBX8 can inhibit PIM1-induced cell senescence. These data suggest that to promote CBX8 degradation may be an important molecular mechanism of PIM1-induced cell senescence.

Increased FoxO3a expression prevents osteoblast differentiation and matrix calcification

Forkhead Box O transcription factors play important roles in bone metabolism by defending against oxidative stress and apoptosis. FoxO3a is of special interest as it is the predominant isoform expressed in bone. In osteoblasts, the administration of 1,25 dihydroxyvitamin D₃ (1,25D₃) increases FoxO3a expression, and alters calcium handling. We therefore queried whether FoxO3a participates in vitamin D-mediated regulation of calcium transport pathways or matrix calcification, independent of reactive oxygen species (ROS) formation. To examine this possibility, we differentiated MC3T3-E1 cells into mature osteoblast-like cells over 7 days. This coincided with an increased ability to mineralize extracellular matrix. FoxO3a expression increased throughout differentiation. 1,25D₃ enhanced both FoxO3a mRNA and protein expression. Immunofluorescence microscopy found increased FoxO3a nuclear localization with differentiation and after treatment with 1,25D₃. Live cell ratiometric imaging with Fura-2AM identified significant L-type calcium channel mediated calcium uptake that was enhanced by 1,25D₃. We observed expression of both Ca_v1.2 and Ca_v1.3, although expression decreased throughout differentiation and was not altered by 1,25D₃ treatment. FoxO3a overexpression reduced calcium uptake and calcium deposition. FoxO3a overexpression also prevented alterations in calcium channel expression and the cell differentiation associated decrease in expression of Runx2 and increased expression of osteocalcin, findings consistent with a failure for the cells to differentiate. Based on both our expression and functional data, we suggest that high levels of FoxO3a prevent osteoblast differentiation and matrix calcification.

MALAT1 via microRNA-17 regulation of insulin transcription is involved in the dysfunction of pancreatic β-cells induced by cigarette smoke extract

Cigarettes contain various chemicals with the potential to influence metabolic health. Exposure to cigarette smoke causes a dysfunction in pancreatic β-cells and impairs insulin production. However, the mechanisms for cigarette smoke-induced reduction of insulin remain largely unclear. Data from 558 patients with diabetes showed that, with smoking pack-years, homeostatic model assessment (HOMA)-β (a method for assessing β-cell function) decreased and that HOMA of insulin resistance increased. For β-cells (MIN6), cigarette smoke extract (CSE) increased the levels of thioredoxin-interacting protein (TXNIP) and the long noncoding (lnc)RNA, metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), and downregulated the levels of the transcription factor, mafA, and microRNA (miR)-17. MALAT1, one of four lncRNAs predicted to regulate miR-17, was knocked down by small interfering RNA (siRNA). For these cells, an miR-17 mimic inhibited TXNIP and enhanced the production of insulin. Knockdown of MALAT1 induced an increase in miR-17, which suppressed TXNIP and promoted the production of insulin. In the sera of patients with diabetes who smoked, there were higher MALAT1 levels and lower miR-17 levels than in the sera of nonsmokers. Thus, CSE inhibits insulin production by upregulating TXNIP via MALAT1-mediated downregulation of miR-17, which provides an understanding of the processes involved in the reduced β-cells function caused by cigarette smoke.

The Function of Thioredoxin-Binding Protein-2 (TBP-2) in Different Diseases

Thioredoxin-binding protein-2 (TBP-2) has an important role in the redox system, but it plays a different role in many different diseases (e.g., various cancers, diabetes mellitus (DM), cardiovascular disease, and cataracts) by influencing cell proliferation, differentiation, apoptosis, autophagy, and metabolism. Distinct transcription factors (TFs) stimulated by different factors combine with binding sites or proteins to upregulate or downregulate TBP-2 expression, in order to respond to the change in the internal environment. Most research disclosed that the main function of TBP-2 is associating with thioredoxin (Trx) to inhibit the antioxidant capacity of Trx. Furthermore, the TBP-2 located in tissues, whether normal or abnormal, has the ability to cause the dysfunctioning of cells and even death through different pathways, such as shortening the cell cycle and inducing apoptosis or autophagy. Through these studies, we found that TBP-2 promoted the development of diseases which are involved in inflammatory and oxidative damage. To a certain extent, we believe that there is some hidden connection between the biological functions which TBP-2 participates in and some distinct diseases. This review presents only a summary of the roles that TBP-2 plays in cancer, DM, cataracts, and so on, as well as its universal mechanisms. Further investigations are needed for the cell signaling pathways of the effects caused by TBP-2. A greater understanding of the mechanisms of TBP-2 could produce potential new targets for the treatment of diseases, including cancer and diabetes, cardiovascular disease, and cataracts.

IRE1α inhibition decreased TXNIP/NLRP3 inflammasome activation through miR-17-5p after neonatal hypoxic-ischemic brain injury in rats

Background

The endoplasmic reticulum (ER) is responsible for the control of correct protein folding and protein function which is crucial for cell survival. However, under pathological conditions, such as hypoxia–ischemia (HI), there is an accumulation of unfolded proteins thereby triggering the unfolded protein response (UPR) and causing ER stress which is associated with activation of several stress sensor signaling pathways, one of them being the inositol requiring enzyme-1 alpha (IRE1α) signaling pathway. The UPR is regarded as a potential contributor to neuronal cell death and inflammation after HI. In the present study, we sought to investigate whether microRNA-17 (miR-17), a potential IRE1α ribonuclease (RNase) substrate, arbitrates downregulation of thioredoxin-interacting protein (TXNIP) and consequent NLRP3 inflammasome activation in the immature brain after HI injury and whether inhibition of IRE1α may attenuate inflammation via miR-17/TXNIP regulation.

Methods

Postnatal day 10 rat pups (n = 287) were subjected to unilateral carotid artery ligation followed by 2.5 h of hypoxia (8% O₂). STF-083010, an IRE1α RNase inhibitor, was intranasally delivered at 1 h post-HI or followed by an additional one administration per day for 2 days. MiR-17-5p mimic or anti-miR-17-5p inhibitor was injected intracerebroventricularly at 48 h before HI. Infarct volume and body weight were used to evaluate the short-term effects while brain weight, gross and microscopic brain tissue morphologies, and neurobehavioral tests were conducted for the long-term evaluation. Western blots, immunofluorescence staining, reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), and co-immunoprecipitation (Co-IP) were used for mechanism studies.

Results

Endogenous phosphorylated IRE1α expression was significantly increased after HI. Intranasal administration of STF-083010 alleviated brain injury and improved neurological behavior. MiR-17-5p expression was reduced after HI, and this decrease was attenuated by STF-083010 treatment. MiR-17-5p mimic administration ameliorated TXNIP expression, NLRP3 inflammasome activation, caspase-1 cleavage, and IL-1β production, as well as brain infarct volume. Conversely, anti-miR-17-5p inhibitor reversed IRE1α inhibition-induced decrease in TXNIP expression and inflammasome activation, as well as exacerbated brain injury after HI.

Conclusions

IRE1a-induced UPR pathway may contribute to inflammatory activation and brain injury following neonatal HI. IRE1a activation, through decay of miR-17-5p, elevated TXNIP expression to activate NLRP3 inflammasome and aggravated brain damage.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1077-9) contains supplementary material, which is available to authorized users.

FoxO transcription factors in cancer metabolism

FoxO transcription factors serve as the central regulator of cellular homeostasis and are tumor suppressors in human cancers. Recent studies have revealed that, besides their classic functions in promoting cell death and inducing cell cycle arrest, FoxOs also regulate cancer metabolism, an emerging hallmark of cancer. In this review, we summarize the regulatory mechanisms employed to control FoxO activities in the context of cancer biology, and discuss FoxO function in metabolism reprogramming in cancer and interaction with other key cancer metabolism pathways. A deeper understanding of FoxOs in cancer metabolism may reveal novel therapeutic opportunities in cancer treatment.

PIM1 induces cellular senescence through phosphorylation of UHRF1 at Ser311

PIM1 is a proto-oncogene, encoding a serine/threonine protein kinase that regulates cell proliferation, survival, differentiation and apoptosis. Previous reports suggest that overexpression of PIM1 can induce cellular senescence. However, the molecular mechanism underlying this process is not fully understood. Here we report that UHRF1 is a novel substrate of PIM1 kinase, which could be phosphorylated at Ser311 and therefore promoted to degradation. Our data demonstrates that PIM1 destabilizes UHRF1, leading to DNA hypomethylation, which consequently results in genomic instability, increased p16 expression and subsequent induction of cellular senescence. Taken together, our results suggest that down-regulation of UHRF1 is an important mechanism of PIM1-mediated cellular senescence.

Vascular endothelial cells senescence is associated with NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation via reactive oxygen species (ROS)/thioredoxin-interacting protein (TXNIP) pathway

Endothelial dysfunction caused by endothelial cells senescence and chronic inflammation is tightly linked to the development of cardiovascular diseases. NLRP3 (NOD-like receptor family pyrin domain-containing3) inflammasome plays a central role in inflammatory response that is associated with diverse inflammatory diseases. This study explores the effects and possible mechanisms of NLRP3 inflammasome in endothelial cells senescence. Results show an increment of pro-inflammatory cytokine interleukin (IL) -1β secretion and caspase-1 activation during the senescence of endothelial cells induced by bleomycin. Moreover, secreted IL-1β promoted endothelial cells senescence through up-regulation of p53/p21 protein expression. NLRP3 inflammasome was found to mediate IL-1β secretion through the production of ROS (reactive oxygen species) during the senescence of endothelial cells. Furthermore, the association of TXNIP (thioredoxin-interacting protein) with NLRP3 induced by ROS promoted NLRP3 inflammasome activation in senescent endothelial cells. In addition, the expressions of NLRP3 inflammasome related genes, ASC (apoptosis associated speck-like protein containing a CARD), TXNIP, cleaved caspase-1 and IL-1β, were also increased in vitro and in vivo studies. These findings indicate that endothelial senescence could be mediated through ROS and NLRP3 inflammasome signaling pathways, suggesting a potential target for the prevention of endothelial senescence-related cardiovascular diseases.

Cytokines Regulate β-Cell Thioredoxin-interacting Protein (TXNIP) via Distinct Mechanisms and Pathways

Thioredoxin-interacting protein (TXNIP) is a key regulator of diabetic β-cell apoptosis and dysfunction, and TXNIP inhibition prevents diabetes in mouse models of type 1 and type 2 diabetes. Although we have previously shown that TXNIP is strongly induced by glucose, any regulation by the proinflammatory cytokines tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), and interferon γ (IFNγ) has remained largely unexplored. Moreover, even though this three-cytokine mixture is widely used to mimic type 1 diabetes in vitro, the mechanisms involved are not fully understood. Interestingly, we have now found that this cytokine mixture increases β-cell TXNIP expression; however, although TNFα had no effect, IL-1β surprisingly down-regulated TXNIP transcription, whereas IFNγ increased TXNIP levels in INS-1 β-cells and primary islets. Human TXNIP promoter analyses and chromatin immunoprecipitation studies revealed that the IL-1β effect was mediated by inhibition of carbohydrate response element binding protein activity. In contrast, IFNγ increased pro-apoptotic TXNIP post-transcriptionally via induction of endoplasmic reticulum stress, activation of inositol-requiring enzyme 1α (IRE1α), and suppression of miR-17, a microRNA that targets and down-regulates TXNIP. In fact, miR-17 knockdown was able to mimic the IFNγ effects on TXNIP, whereas miR-17 overexpression blunted the cytokine effect. Thus, our results demonstrate for the first time that the proinflammatory cytokines TNFα, IL-1β, and IFNγ each have distinct and in part opposing effects on β-cell TXNIP expression. These findings thereby provide new mechanistic insight into the regulation of TXNIP and β-cell biology and reveal novel links between proinflammatory cytokines, carbohydrate response element binding protein-mediated transcription, and microRNA signaling.

Senescence-associated Long Non-coding RNA (SALNR) Delays Oncogene-induced Senescence through NF90 Regulation

Long non-coding RNAs (lncRNAs) have recently emerged as key players in many physiologic and pathologic processes. Although many lncRNAs have been identified, few lncRNAs have been characterized functionally in aging. In this study, we used human fibroblast cells to investigate genome-wide lncRNA expression during cellular senescence. We identified 968 down-regulated lncRNAs and 899 up-regulated lncRNAs in senescent cells compared with young cells. Among these lncRNAs, we characterized a senescence-associated lncRNA (SALNR), whose expression was reduced during cellular senescence and in premalignant colon adenomas. Overexpression of SALNR delayed cellular senescence in fibroblast cells. Furthermore, we found that SALNR interacts with NF90 (nuclear factor of activated T-cells, 90 kDa), an RNA-binding protein suppressing miRNA biogenesis. We demonstrated that NF90 is a SALNR downstream target, whose inhibition led to premature senescence and enhanced expressions of senescence-associated miRNAs. Moreover, our data showed that Ras-induced stress promotes NF90 nucleolus translocation and suppresses its ability to suppress senescence-associated miRNA biogenesis, which could be rescued by SALNR overexpression. These data suggest that lncRNA SALNR modulates cellular senescence at least partly through changing NF90 activity.

NQO1 Stabilizes p53 in Response to Oncogene-Induced Senescence

Cellular senescence is a state of permanent cellular arrest that provides an initial barrier to cell transformation and tumorigenesis. In this study, we report that expression of NAD(P)H:quinone oxidoreductase 1 (NQO1), a cytoplasmic 2-electron reductase, is induced during oncogene-induced senescence (OIS). Depletion of NQO1 resulted in the delayed onset of senescence. In contrast, ectopic expression of NQO1 enhanced the senescence phenotype. Analysis of the mechanism underlying the up-regulation of NQO1 expression during senescence identified that NQO1 promotes p53 accumulation in an MDM2 and ubiquitin independent manner, which reinforces the cellular senescence phenotype. Specifically, we demonstrated that NRF2/KEAP1 signaling regulates NQO1 expression during OIS. More importantly, we confirmed that depletion of NQO1 facilitates cell transformation and tumorigenesis, which indicates that NQO1 takes part in the senescence barrier and has anti-oncogenic properties in cell transformation.

C/EBPβ promotes angiogenesis through secretion of IL-6, which is inhibited by genistein, in EGFRvIII-positive glioblastoma

To study the mechanisms underlying the IL-6-promoted angiogenic microenvironment in EGFRvIII-positive glioblastoma, VEGF expression in EGFRvIII-positive/negative tumors was determined by optical molecular imaging. Next, the HUVEC tube formation assay, Western blot, qPCR, RNA silencing, chromatin immunoprecipitation, luciferase reporter and ELISA assays were performed to examine the role of IL-6 and C/EBPβ in the formation of the angiogenic microenvironment in EGFRvIII-positive tumors. Finally, in vitro and in vivo genistein treatment experiments were conducted to challenge the interaction between the IL-6 promoter and C/EBPβ. Optical imaging revealed greater VEGF expression in EGFRvIII-positive tumor-bearing mice, suggesting an angiogenic microenvironment. In vitro experiments demonstrated that C/EBPβ-mediated regulation of IL-6 was indispensable for maintenance of this angiogenic microenvironment. In contrast, genistein-mediated upregulation of CHOP impeded C/EBPβ interaction with the IL-6 promoter, thus disturbing the angiogenic microenvironment. This more malignant microenvironment in EGFRvIII glioblastoma is generated, at least in part, by greater VEGF, IL-6 and C/EBPβ expression. Interaction of C/EBPβ with the IL-6 promoter maintains this angiogenic microenvironment, while disturbance of this dynamically balanced interaction inhibits EGFRvIII tumor proliferation by reducing both VEGF and IL-6 expression.

PIM-1 modulates cellular senescence and links IL-6 signaling to heterochromatin formation

Cellular senescence is a stable state of proliferative arrest that provides a barrier against malignant transformation and contributes to the antitumor activity of certain chemotherapies. Unexpectedly, we found that the expression of proto-oncogene PIM-1, which can promote tumorigenesis, is induced at transcriptional level during senescence. Inhibition of PIM-1 alleviated both replicative and oncogene-induced senescence. Conversely, ectopic expression of PIM-1 resulted in premature senescence. We also revealed that PIM-1 interacts with and phosphorylates heterochromatin protein 1γ (HP1γ) on Ser93. This PIM-1-mediated HP1γ phosphorylation enhanced HP1γ's capacity to bind to H3K9me3, resulting in heterochromatin formation and suppression of proliferative genes, such as CCNA2 and PCNA. Analysis of the mechanism underlying the up-regulation of PIM-1 expression during senescence demonstrated that IL-6, a critical regulator of cellular senescence, is responsible for PIM-1 induction. Our study demonstrated that PIM-1 is a key component of the senescence machinery that contributes to heterochromatin formation. More importantly, we demonstrated that PIM-1 is also a direct target of IL-6/STAT3 signaling and mediates cytokine-induced cellular senescence.

Thioredoxin as a putative biomarker and candidate target in age-related immune decline

The oxidoreductase Trx-1 (thioredoxin 1) is highly conserved and found intra- and extra-cellularly in mammalian systems. There is increasing interest in its capacity to regulate immune function based on observations of altered distribution and expression during ageing and disease. We have investigated previously whether extracellular T-cell or peripheral blood mononuclear cell Trx-1 levels serve as a robust marker of ageing. In a preliminary study of healthy older adults compared with younger adults, we showed that there was a significant, but weak, relationship with age. Interestingly, patients with rheumatoid arthritis and cancer have been described by others to secrete or express greater surface Trx-1 than predicted. It is interesting to speculate whether a decline in Trx-1 during ageing protects against such conditions, but correspondingly increases risk of disease associated with Trx-1 depletion such as cardiovascular disease. These hypotheses are being explored in the MARK-AGE study, and preliminary findings confirm an inverse correlation of surface Trx-1 with age. We review recent concepts around the role of Trx-1 and its partners in T-cell function on the cell surface and as an extracellular regulator of redox state in a secreted form. Further studies on the redox state and binding partners of surface and secreted Trx-1 in larger patient datasets are needed to improve our understanding of why Trx-1 is important for lifespan and immune function.

Minireview: Thioredoxin-interacting protein: regulation and function in the pancreatic β-cell

Pancreatic β-cells are responsible for insulin production, and loss of functional β-cell mass is now recognized as a critical step in the pathogenesis of both type 1 and type 2 diabetes. However, the factors controlling the life and death of the pancreatic β-cell have only started to be elucidated. Discovered as the top glucose-induced gene in a human islet microarray study 12 years ago, thioredoxin-interacting protein (TXNIP) has now emerged as such a key player in pancreatic β-cell biology. Since then, β-cell expression of TXNIP has been found to be tightly regulated by multiple factors and to be dramatically increased in diabetic islets. Elevated TXNIP levels induce β-cell apoptosis, whereas TXNIP deficiency protects against type 1 and type 2 diabetes by promoting β-cell survival. TXNIP interacts with and inhibits thioredoxin and thereby controls the cellular redox state, but it also belongs to the α-arrestin family of proteins and regulates a variety of metabolic processes. Most recently, TXNIP has been discovered to control β-cell microRNA expression, β-cell function, and insulin production. In this review, the current state of knowledge regarding regulation and function of TXNIP in the pancreatic β-cell and the implications for drug development are discussed.

The mitogen-inducible gene-6 is involved in regulation of cellular senescence in normal diploid fibroblasts

BACKGROUND INFORMATION

The mitogen-inducible gene-6 (Mig-6) is a non-kinase scaffolding adaptor protein. It has been shown that Mig-6 may play important roles in regulating stress response, maintaining homeostasis and functioning as a tumour suppressor. In this study, we investigated the role of Mig-6 in cellular senescence.

RESULTS

Our results showed that Mig-6 is up-regulated during the senescence process. Functional analysis indicated that cells over-expressing Mig-6 have reduced DNA synthesis and showed the signs of senescence. Knockdown of Mig-6 delayed the initiation of Ras-induced cellular senescence. These results suggest that the increase of Mig-6 expression contributes to establishment of cellular senescence. Furthermore, our results showed that Mig-6 induction of senescence is related to its inhibition of EGF receptor (EGFR)/Erb B signalling. Subsequent analysis of the mechanism responsible for the up-regulation of its expression showed that FOXO3A transcriptionally up-regulates Mig-6 expression via directly binding to the FOXO response element in Mig-6 5'-flanking regulatory sequences.

CONCLUSIONS

Mig-6 induces premature senescence via functioning in regulation of cellular senescence in normal diploid fibroblasts.

TXNIP maintains the hematopoietic cell pool by switching the function of p53 under oxidative stress

Reactive oxygen species (ROS) are critical determinants of the fate of hematopoietic stem cells (HSCs) and hematopoiesis. Thioredoxin-interacting protein (TXNIP), which is induced by oxidative stress, is a known regulator of intracellular ROS. Txnip(-/-) old mice exhibited elevated ROS levels in hematopoietic cells and showed a reduction in hematopoietic cell population. Loss of TXNIP led to a dramatic reduction of mouse survival under oxidative stress. TXNIP directly regulated p53 protein by interfering with p53- mouse double minute 2 (MDM2) interactions and increasing p53 transcriptional activity. Txnip(-/-) mice showed downregulation of the antioxidant genes induced by p53. Introduction of TXNIP or p53 into Txnip(-/-) bone marrow cells rescued the HSC frequency and greatly increased survival in mice following oxidative stress. Overall, these data indicate that TXNIP is a regulator of p53 and plays a pivotal role in the maintenance of the hematopoietic cells by regulating intracellular ROS during oxidative stress.

Thioredoxin and thioredoxin target proteins: from molecular mechanisms to functional significance

The thioredoxin (Trx) system is one of the central antioxidant systems in mammalian cells, maintaining a reducing environment by catalyzing electron flux from nicotinamide adenine dinucleotide phosphate through Trx reductase to Trx, which reduces its target proteins using highly conserved thiol groups. While the importance of protecting cells from the detrimental effects of reactive oxygen species is clear, decades of research in this field revealed that there is a network of redox-sensitive proteins forming redox-dependent signaling pathways that are crucial for fundamental cellular processes, including metabolism, proliferation, differentiation, migration, and apoptosis. Trx participates in signaling pathways interacting with different proteins to control their dynamic regulation of structure and function. In this review, we focus on Trx target proteins that are involved in redox-dependent signaling pathways. Specifically, Trx-dependent reductive enzymes that participate in classical redox reactions and redox-sensitive signaling molecules are discussed in greater detail. The latter are extensively discussed, as ongoing research unveils more and more details about the complex signaling networks of Trx-sensitive signaling molecules such as apoptosis signal-regulating kinase 1, Trx interacting protein, and phosphatase and tensin homolog, thus highlighting the potential direct and indirect impact of their redox-dependent interaction with Trx. Overall, the findings that are described here illustrate the importance and complexity of Trx-dependent, redox-sensitive signaling in the cell. Our increasing understanding of the components and mechanisms of these signaling pathways could lead to the identification of new potential targets for the treatment of diseases, including cancer and diabetes.

MiR-30d induces apoptosis and is regulated by the Akt/FOXO pathway in renal cell carcinoma

MicroRNAs (miRNAs) play critical roles in tumorigenesis by modulating the expression of target gene mRNAs. However, their role in cell signaling is not well defined. In this study, we identified miR-30d as a downstream effector of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway in renal cell carcinoma (RCC) cells. We show that Akt inhibition transcriptionally up-regulates miR-30d expression through activation of the transcription factor forkhead box O (FOXO) 3A. Functional analysis revealed that miR-30d overexpression suppresses cell proliferation and induces apoptosis in RCC cells, suggesting that miR-30d acts as a tumor suppressor. In searching for downstream targets of miR-30d, we found that miR-30d post-transcriptionally suppresses expression of the oncoprotein metadherin (MTDH) by destabilizing its mRNA. Furthermore, we found that FOXO down-regulates MTDH expression through up-regulating expression of miR-30d. Thus, our findings reveal a new Akt/FOXO/miR-30d/MTDH signaling transduction pathway and identify miR-30d as a tumor suppressor, providing a new potential target for the treatment of RCC.

From cellular senescence to age-associated diseases: the miRNA connection

Cellular senescence has evolved from an in-vitro model system to study aging in vitro to a multifaceted phenomenon of in-vivo importance as senescent cells in vivo have been identified and their removal delays the onset of age-associated diseases in a mouse model system. From the large emerging class of non-coding RNAs, miRNAs have only recently been functionally implied in the regulatory networks that are modified during the aging process. Here we summarize examples of similarities between the differential expression of miRNAs during senescence and age-associated diseases and suggest that these similarities might emphasize the importance of senescence for the pathogenesis of age-associated diseases. Understanding such a connection on the level of miRNAs might offer valuable opportunities for designing novel diagnostic and therapeutic strategies.

Spi-1, Fli-1 and Fli-3 (miR-17-92) oncogenes contribute to a single oncogenic network controlling cell proliferation in friend erythroleukemia

Clonal erythroleukemia developing in susceptible mice infected by Friend virus complex are associated with highly recurrent proviral insertions at one of three loci called Spi-1, Fli-1 or Fli-3, leading to deregulated expression of oncogenic Spi-1 or Fli-1 transcription factors or miR-17-92 miRNA cluster, respectively. Deregulated expression of each of these three oncogenes has been independently shown to contribute to cell proliferation of erythroleukemic clones. Previous studies showed a close relationship between Spi-1 and Fli-1, which belong to the same ETS family, Spi-1 activating fli-1 gene, and both Spi-1 and Fli-1 activating multiple common target genes involved in ribosome biogenesis. In this study, we demonstrated that Spi-1 and Fli-1 are also involved in direct miR-17-92 transcriptional activation through their binding to a conserved ETS binding site in its promoter. Moreover, we demonstrated that physiological re-expression of exogenous miR-17 and miR-20a are able to partially rescue the proliferation loss induced by Fli-1 knock-down and identified HBP1 as a target of these miRNA in erythroleukemic cells. These results establish that three of the most recurrently activated oncogenes in Friend erythroleukemia are actually involved in a same oncogenic network controlling cell proliferation. The putative contribution of a similar ETS-miR-17-92 network module in other normal or pathological proliferative contexts is discussed.

The Akt-associated microRNAs

As master gene regulators, microRNAs are involved in diverse cellular pathways. It is well known that microRNAs are often dysregulated in many types of cancer and other human diseases. In cancer, microRNAs may function as oncogenes or tumor suppressors. Interestingly, recent evidence suggests that microRNA-mediated gene regulation interconnects with the Akt pathway, forming an Akt-microRNA regulatory network. MicroRNAs and Akt in this network work together to exert their cellular functions. Thus, a better understanding of this Akt-microRNA regulatory network is critical to successful targeting of the PI3K/Akt pathway for cancer therapy. We review recent advances in the understanding of how microRNAs affect Akt activity as well as how microRNAs are regulated through the Akt pathway. We also briefly discuss the clinical implication of gene regulation mediated through Akt-associated microRNAs.

Specific alterations of the microRNA transcriptome and global network structure in colorectal cancer after treatment with MAPK/ERK inhibitors

The mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) pathway has a master control role in various cancer-related biological processes as cell growth, proliferation, differentiation, migration, and apoptosis. It also regulates many transcription factors that control microRNAs (miRNAs) and their biosynthetic machinery. To investigate on the still poorly characterised global involvement of miRNAs within the pathway, we profiled the expression of 745 miRNAs in three colorectal cancer (CRC) cell lines after blocking the pathway with three different inhibitors. This allowed the identification of two classes of post-treatment differentially expressed (DE) miRNAs: (1) common DE miRNAs in all CRC lines after treatment with a specific inhibitor (class A); (2) DE miRNAs in a single CRC line after treatment with all three inhibitors (class B). By determining the molecular targets, biological roles, network position of chosen miRNAs from class A (miR-372, miR-663b, miR-1226*) and class B (miR-92a-1*, miR-135b*, miR-720), we experimentally demonstrated that they are involved in cell proliferation, migration, apoptosis, and globally affect the regulation circuits centred on MAPK/ERK signaling. Interestingly, the levels of miR-92a-1*, miR-135b*, miR-372, miR-720 are significantly higher in biopsies from CRC patients than in normal controls; they also are significantly higher in CRC patients with mutated KRAS than in those with wild-type genotypes (Wilcoxon test, p < 0.05): the latter could be a downstream effect of ERK pathway overactivation, triggered by KRAS mutations. Finally, our functional data strongly suggest the following miRNA/target pairs: miR-92a-1*/PTEN-SOCS5; miR-135b*/LATS2; miR-372/TXNIP; miR-663b/CCND2. Altogether, these results contribute to deepen current knowledge on still uncharacterized features of MAPK/ERK pathway, pinpointing new oncomiRs in CRC and allowing their translation into clinical practice and CRC therapy.

A crossroad of microRNAs and immediate early genes (IEGs) encoding oncogenic transcription factors in breast cancer

Signaling networks are involved in development, as well as in malignancy of the mammary gland. Distinct external stimuli activate intricate signaling cascades, which culminate in the activation of specific transcriptional programs. These signal-specific transcriptional programs are instigated by transcription factors (TFs) encoded by the immediate early genes (IEGs), and they lead to diverse cellular outcomes, including oncogenesis. Hence, regulating the expression of IEGs is of great importance, and involves several complementary transcriptional and posttranscriptional mechanisms, the latter entails also microRNAs (miRNAs). miRNAs are a class of non-coding RNAs, which have been implicated in regulation of various aspects of signaling networks. Through examination of the basic characteristics of miRNA function, we highlight the benefits of using miRNAs as regulators of early TFs and signaling networks. We further focus on the role of miRNAs as regulators of IEGs, which shape the initial steps of signaling-induced transcription. We especially emphasize the role of miRNAs in buffering external noise and maintaining low basal activation of IEGs in the absence of proper stimuli.

Thioredoxin binding protein (TBP)-2/Txnip and α-arrestin proteins in cancer and diabetes mellitus

Thioredoxin binding protein -2/ thioredoxin interacting protein is an α-arrestin protein that has attracted much attention as a multifunctional regulator. Thioredoxin binding protein -2 expression is downregulated in tumor cells and the level of thioredoxin binding protein is correlated with clinical stage of cancer. Mice with mutations or knockout of the thioredoxin binding protein -2 gene are much more susceptible to carcinogenesis than wild-type mice, indicating a role for thioredoxin binding protein -2 in cancer suppression. Studies have also revealed roles for thioredoxin binding protein -2 in metabolic control. Enhancement of thioredoxin binding protein -2 expression causes impairment of insulin sensitivity and glucose-induced insulin secretion, and β-cell apoptosis. These changes are important characteristics of type 2 diabetes mellitus. Thioredoxin binding protein -2 regulates transcription of metabolic regulating genes. Thioredoxin binding protein -2-like inducible membrane protein/ arrestin domain containing 3 regulates endocytosis of receptors such as the β(2)-adrenergic receptor. The α-arrestin family possesses PPXY motifs and may function as an adaptor/scaffold for NEDD family ubiquitin ligases. Elucidation of the molecular mechanisms of α-arrestin proteins would provide a new pharmacological basis for developing approaches against cancer and type 2 diabetes mellitus.